From 3f17f528d1cf54d439e911c74257579592c99e16 Mon Sep 17 00:00:00 2001
From: Alx Sa <cmyk.student@gmail.com>
Date: Mon, 23 Mar 2026 20:27:38 +0000
Subject: [PATCH] plug-ins: Load more multichannel PSD channels

Multichannel PSD images reuse their first channel as the
main grayscale "layer". Our PSD plug-in did not take this
into account, resulting in the channels being off-by-one and
mislabeled.

This patch prevents chn_a[0].data from being freed after
it is used to load the layer, and then resets the counts so that
it is reused as the first imported channel.
---
 plug-ins/file-psd/psd-load.c | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/plug-ins/file-psd/psd-load.c b/plug-ins/file-psd/psd-load.c
index 0cbaa25492..d9a24829f7 100644
--- a/plug-ins/file-psd/psd-load.c
+++ b/plug-ins/file-psd/psd-load.c
@@ -3153,7 +3153,11 @@ add_merged_image (GimpImage     *image,
               memcpy (&pixels[((i * base_channels) + cidx) * bps],
                       &chn_a[cidx].data[i * bps], bps);
             }
-          g_free (chn_a[cidx].data);
+
+          /* For multichannel images, the first layer is also
+           * the first channel, so we don't want to free it yet */
+          if (img_a->color_mode != PSD_MULTICHANNEL)
+            g_free (chn_a[cidx].data);
         }
 
       /* Add background layer */
@@ -3241,9 +3245,12 @@ add_merged_image (GimpImage     *image,
   else
     {
       /* Free merged image data for layered image */
-      if (extra_channels)
-        for (cidx = 0; cidx < base_channels; ++cidx)
-          g_free (chn_a[cidx].data);
+      if (extra_channels &&
+          img_a->color_mode != PSD_MULTICHANNEL)
+        {
+          for (cidx = 0; cidx < base_channels; ++cidx)
+            g_free (chn_a[cidx].data);
+        }
     }
 
   if (img_a->transparency)
@@ -3257,6 +3264,14 @@ add_merged_image (GimpImage     *image,
         }
     }
 
+  /* Multichannel mode uses the first channel as the grayscale layer,
+   * so we need to reset the index to grab it again */
+  if (img_a->color_mode == PSD_MULTICHANNEL)
+    {
+      base_channels  = 0;
+      extra_channels = img_a->alpha_id_count;
+    }
+
   /* ----- Draw extra alpha channels ----- */
   if (extra_channels                   /* Extra alpha channels */
       && image)